The present invention relates to a boat propeller. More particularly this invention concerns such a propeller specifically designed so that its vanes can be replaced in the field.
A standard variable-pitch propeller has a hub centered on and rotatable about a hub axis and formed with a plurality of radially outwardly open pockets each having a predetermined inside diameter and each centered on a respective vane axis extending generally radially of the hub axis. A mounting plate rotatable in the pocket about the vane axis is held therein by a ring fixed in the pocket. A vane extending along the vane axis has a base fitting in the pocket on the face of the plate. Pivoting of the plate about the respective vane axis pivots the vane to change the propeller pitch.
The vanes are pivoted by respective jointly axially displaceable rods that are exposed in the pockets and sealed to both sides of the pockets. Eccentric formations on the plates engage the rods so that, when same are shifted axially, the plates turn about the respective vane axes.
The bases of the vanes are normally secured by one or more screws to the respective plates so that they can, if necessary, be removed and replaced. Each vane base is provided with a seal ring that bears on the inner surface of the respective pocket so that water cannot enter the interior of the hub.
If a vane gets damaged, for instance by hitting the bottom or an object in the water, it must be replaced. The boat must be at least partially lifted out of the water, as once the vane is removed the interior of the hub is completely open, and it cannot be allowed to fill with water. When the hub is replaced the new seal must be meticulously installed to prevent leakage.
Even with the most care, the vane seals fail occasionally, in particular since they are deformed as the propeller pitch changes. Thus periodic failure and exposure of the interior of the hub to water is likely.
It is therefore an object of the present invention to provide an improved variable-pitch boat propeller.
Another object is the provision of such an improved variable-pitch boat propeller which overcomes the above-given disadvantages, that is whose vanes can be easily replaced, even under water, and where the likelihood of leakage into the hub is largely eliminated.
A variable-pitch boat propeller has according to the invention a hub centered on and rotatable about a hub axis and formed with a radially outwardly open pocket having a predetermined inside diameter and centered on a vane axis extending generally radially of the hub axis and a mounting plate rotatable in the pocket about the vane axis and having an outer face. A ring fixed in the pocket and having inner and outer peripheries bears radially inward of the hub axis on the mounting plate. An inner seal is provided between the inner ring periphery and the plate and an outer seal between the outer ring periphery and the pocket. A vane extending along the vane axis has a base of an outside diameter smaller than the inside diameter of the pocket and fitting in the pocket on the face of the plate. A screw or the like releasably secures the vane base to the plate face, and mechanism pivots the plate in the pocket about the vane axis.
Thus with this system the sealing is not done between the vane base and the hub pocket, but between the ring holding the plate in place and, on the outside, the pocket and, on the inside, the plate. This ring is normally installed in the factory or is only dealt with by professionals, normally in dry dock, so that its seals can be counted on to be installed perfectly and work without problems. The vane can, however, be unbolted and replaced by anyone with tools, even under water, with no likelihood of compromising the seals.
The pocket according to the invention is cylindrically stepped and centered on the vane axis. The ring has a flange engaging radially inward of the vane axis and overreaching an outer edge of the plate. Normally the inner portion of the stepped pocket is threaded so that the ring, which is externally threaded, can be screwed solidly into place.
The seal in accordance with the invention is between the flange and the plate and bears radially of the vane axis on the flange and the plate. The pocket has a floor and the ring has an axial flange bearing around the plate on the floor. The ring is of L-section and the seals are O-rings.